Pochettino's 44th birthday did not bring him the three points he doubtless wanted
Michail Antonio's seventh-minute header from Dimitri Payet's corner proved to be the difference between the two sides in Spurs' last ever game at Upton Park.
Pochettino did not name Dele Alli in the starting line-up and Spurs produced a nervy display as they were unable to break the Hammers down.
"I think that we didn’t start the game in a good way," Pochettino said.
"We made some mistakes and the team didn’t feel free to play the way they play.
"West Ham is a strong, physical team which made it difficult and the conditions favoured them because the pitch wasn’t good.
“We need to be positive and it is important to be ready for Saturday.
"When you lose you can blame that the players are tired or whatever but the reality is that it was just a bad night for us to play the way we play tonight."
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With Leicester's failure to beat West Brom on Tuesday and Arsenal losing to Swansea, the game turned out to be a chance for Spurs to put their stamp on the Premier League title race.
And while Pochettino was disappointed not to take the chance to go top of the table, he could not fault his players' work ethic.
“The players are sad and it is true that we are very motivated and excited to stay towards the top of the table," Pochettino added.
"I feel proud of them as the effort was fantastic.”